土石混合体细观渗流场的格子Boltzmann模拟

Numerical Simulation of Mesoscopic Seepage Field of Soil-rock Mixture Based on Lattice Boltzmann Method

基于土石混合体中块石的CT扫描图片、颗粒流PFC软件及数字图像处理技术构建了土石混合体的孔隙结构模型,在此基础上引入介观的格子Boltzmann方法从孔隙尺度对土石混合体的渗流场进行了数值模拟,并据此分析了土石混合体的渗流特性。研究结果表明:基于土石混合体的孔隙结构模型和介观的格子Boltzmann方法,通过设置相应的边界条件可以快速有效地模拟土石混合体的细观渗流机制;与均质土体模型相比,土石混合体模型由于较大块石的存在使得其渗流通道明显减少,且通道变窄,弯折度增加,流速减小,渗透率大幅降低;土石混合体模型中水压力分布很不均匀,在块石的上下游会发生显著的压力降;块石含量、块石粒径及块石空间分布等细观结构因素对土石混合体的渗流场与渗透性能有一定的影响。

Based on the CT scanning images for rock blocks in soil-rock mixture( SRM),the particle flow code software PFC2 D and the digital image processing technology,the pore-structural models of SRM were constructed.The mesoscopic lattice Boltzmann method was introduced to simulate the seepage field of the constructed pore-structural models and the seepage characteristics of SRM were analyzed. The results show that the mesoscopic seepage mechanisms of SRM can be quickly and effectively simulated by using the lattice Boltzmann method on the porestructural models of SRM with corresponding boundary conditions. Compared with the homogeneous soil model,due to the existence of large rock blocks,the SRM models have much fewer,narrower and tortuous seepage channels,which result in a slower flow velocity and thus a significantly reduced permeability. In SRM models,the flow pressure distribution is very uneven and a significant pressure drop occurs between the upstream and downstream of the rock blocks. The seepage field and permeability of SRM are affected by the meso-structural factors such as the rock block proportion,the rock block size and the spatial distribution of rock blocks.